pybind11 VS PEGTL

I'm investigating using C++ to build a REST server, and would love to know of people's experiences with Crow-- or whether they would recommend something else as a "medium-level" abstraction C++ web server. As background, I started off experimenting with Python/FastAPI, which is great, but there is too much friction to translate from pybind11-exported C++ objects to the format that FastAPI expects, and, of course, there are inherent performance limitations using Python, which could impact scaling up if the project were to be successful.

I have a C++ function computing a large tensor which I would like to return to Python as a NumPy array via pybind11.

This is based on the Google Ink Stroke Modeler C++ library, and using pybind11 to make it available on python.

pybind11 makes it easy to call C++ from Python if you want to mix.

If you've never used Pybind before these pybind tests[1] and this repo[2] have good examples you can crib to get started (in addition to the docs). Once you handle passing/returning/creating the main data types (list, tuple, dict, set, numpy array) the first time, then it's mostly smooth sailing.

Pybind offers a lot of functionality, but core "good parts" I've found useful are (a) use a numpy array in Python and pass it to a C++ method to work on, (b) pass your python data structure to pybind and then do work on it in C++ (some copy overhead), and (c) Make a class/struct in C++ and expose it to Python (so no copying overhead and you can create nice cache-aware structs, etc.).

[1] https://github.com/pybind/pybind11/blob/master/tests/test_py...

I have a python module for which the logic is written in C++ and I use pybind11 to expose the objects and functions to Python.

Reading from Python requires a wrapper, using pybind11 this is fairly done.

Very cool, and I like the name!

I'd be interested in reading about how Matcheroni compares with PEGTL and Lexy.

https://github.com/taocpp/PEGTL

I found a library I wanted to test: Pegtl

I like PEGTL

Sure - libraries that are expected to be entirely self-contained. The one that comes to mind is PEGTL, a parser combinator library that is intended to be embedded inside a larger program. Making it import more dependencies would break this philosophy. Similarly, in the Rust world, there are a variety of "no-std" crates that should be able to be imported even if the standard library is not available on the target platform.

The program in the post was just an example meant to illustrate the problem. Originally, this (new) behavior of MSVC broke my code in the PEGTL, see [this commit](https://github.com/taocpp/PEGTL/commit/e3c8cb499dc3d1d76d23f2d5d79469dcb15550c5) that I needed to apply to fix it.

As a professional C++ programmer I feel a lot of the reasons C++ gets this response is because it's simply not "batteries included" like Go or Rust.

C++ is a very powerful, unopinionated language, that gives you a lot of freedom to attack your problem domain the way you best see fit.

If you're writing a networked application, don't use POSIX sockets, go and find a higher level library. If you're parsing complex text formats, don't iterate over buffers with char*'s, go pick up PEGTL[0]. If you're working on graphs, or need to properly index in-memory data, go pick up Boost[1][2]. If you need a GUI, go pick up Qt.

It's extremely common in C++, due to the lack of a universal package management solution, for people to try and "muddle through" and do shit themselves when it's far outside their core competency.

At one of my last employers, the core product was parsing JSON with std::regex, simply because they couldn't be bothered to integrate a JSON library.

[0] https://github.com/taocpp/PEGTL

[1] https://www.boost.org/doc/libs/1_76_0/libs/graph/

[2] https://www.boost.org/doc/libs/1_76_0/libs/multi_index/doc/i...

You are looking for Boost.Spirit (https://www.boost.org/doc/libs/1_76_0/libs/spirit/doc/x3/html/index.html) or PEGTL (https://github.com/taocpp/PEGTL)

I personally prefer to use parsing combinator libraries in C++, where the "grammar" is just part of normal C++ and directly integrate. Examples are Boost.Spirit, pegtl, or (my own) lexy.

While I'm not quite sure how this might transfer to your approach, with your Haskell-inspired style being quite different from our C++ templates, in the PEGTL our equivalent to your Char, which is called one, is variadic (true to the T in PEGTL a variadic template) and takes a list of possible matches.